title: Microbial ecology dynamics during rye and wheat sourdough preparation.
abstract: The bacterial ecology during rye and wheat sourdough preparation was described by 16S rRNA gene pyrosequencing. Viable plate counts of presumptive lactic acid bacteria, the ratio between lactic acid bacteria and yeasts, the rate of acidification, a permutation analysis based on biochemical and microbial features, the number of operational taxonomic units (OTUs), and diversity indices all together demonstrated the maturity of the sourdoughs during 5 to 7 days of propagation. Flours were mainly contaminated by metabolically active genera (Acinetobacter, Pantoea, Pseudomonas, Comamonas, Enterobacter, Erwinia, and Sphingomonas) belonging to the phylum Proteobacteria or Bacteroidetes (genus Chryseobacterium). Their relative abundances varied with the flour. Soon after 1 day of propagation, this population was almost completely inhibited except for the Enterobacteriaceae. Although members of the phylum Firmicutes were present at very low or intermediate relative abundances in the flours, they became dominant soon after 1 day of propagation. Lactic acid bacteria were almost exclusively representative of the Firmicutes by this time. Weissella spp. were already dominant in rye flour and stably persisted, though they were later flanked by the Lactobacillus sakei group. There was a succession of species during 10 days of propagation of wheat sourdoughs. The fluctuation between dominating and subdominating populations of L. sakei group, Leuconostoc spp., Weissella spp., and Lactococcus lactis was demonstrated. Other subdominant species such as Lactobacillus plantarum were detectable throughout propagation. As shown by PCR-denaturing gradient gel electrophoresis (PCR-DGGE) analysis, Saccharomyces cerevisiae dominated throughout the sourdough propagation. Notwithstanding variations due to environmental and technology determinants, the results of this study represent a clear example of how the microbial ecology evolves during sourdough preparation.
authors.affiliation: Department of Agricultural Sciences, Division of Microbiology, University of Naples Federico II, Portici, Italy.
authors.forename: Danilo
authors.initials: D
authors.lastname: Ercolini
authors.forename: Erica
authors.initials: E
authors.lastname: Pontonio
authors.forename: Francesca
authors.initials: F
authors.lastname: De Filippis
authors.forename: Fabio
authors.initials: F
authors.lastname: Minervini
authors.forename: Antonietta
authors.initials: A
authors.lastname: La Storia
authors.forename: Marco
authors.initials: M
authors.lastname: Gobbetti
authors.forename: Raffaella
authors.initials: R
authors.lastname: Di Cagno
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000235:genetics; D058448:Biota; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D005516:Food Microbiology; D005658:Fungi / Q000145:classification* / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D012434:Secale; D017422:Sequence Analysis, DNA; D013997:Time Factors; D014908:Triticum
chemical_list: D004269:DNA, Bacterial; D004271:DNA, Fungal